Resin materials such as acrylonitrile-butadiene-styrene copolymer (ABS) or polycarbonate, which can achieve superior surface appearance and low warping of a molded article, and metal materials such as magnesium alloys, which have the lowest specific gravity among practical metals while also having high strength, are widely used as materials for the cases of portable electric and electronic devices typically represented by cellular telephones, PDAs and notebook PCs. In recent years, the materials used for the cases of the portable electric and electronic devices are required to have high specific strength. For example, in a case of cellular telephones, materials used for the cases of cellular telephones are required to have high specific strength since cellular telephones have come to be required to be provided with smaller cases and larger liquid crystal displays.
However, cases composed of conventionally used materials such as ABS or polycarbonate lack adequate strength of the material itself, requiring that the lack of strength be compensated for by increasing the thickness of the case. Thus, the thickness of device cases is currently moving in the opposite direction from current demands. In addition, although magnesium alloys have superior strength, the superior electromagnetic shielding property of the magnesium alloys ends up conversely being a disadvantage since these alloys cannot be applied to devices containing a built-in antenna due to the excellent electromagnetic shielding property of the alloys. In addition, magnesium alloys have a higher specific gravity than plastic materials, while also having the problem of higher costs.
In contrast, since polyphenylene sulfide resin (abbreviated as “PPS resin”) has properties that are favorable for use as an engineering plastic such as superior heat resistance, rigidity, dimensional stability and flame resistance, it is widely used primarily for injection molding in various electric and electronic parts, mechanical parts, automotive parts and the like. Therefore, the applications of BPS resin have increased in recent years, and their application is also being examined for functional parts like those exposed to the outside such as the case materials of portable electric and electronic devices as described above. However, the adhesion of DPS resin to other materials is inferior. Therefore, when the PPS resin is applied to functional parts like those exposed on the outside such as the case materials of portable electric and electronic devices and the surface thereof is modified by any of ordinary secondary processing such as coating or vapor deposition, the coated film of PPS resin separates easily due to the poor adhesion between the PPS resin and other materials, and adequate surface secondary processability is not achieved even if the PPS resin surface is coated with a primer.
Therefore, as an example of a technology for carrying out secondary processing on the surface of BPS resin molded articles, a technology is proposed wherein the surface of a PPS resin molded article is made rough by sandblasting or shotblasting and the like followed by coating with a primer (seer for example, Patent Document 1).
However, in methods involving sandblasting or shotblasting the surface of a BPS resin molded article followed by coating with a primer as described above, it is necessary to include a step for roughening the surface of the PPS resin molded article, and device production time and costs increase. Accordingly, this method has extremely disadvantage in industrial production.
On the other hand, regarding a technology for coating chlorinated polyolefin onto the surface of a PPS resin molded articles Patent Document 2 indicated below describes that chlorinated polyolefin can be coated onto the surface of a PPS pipe. However, typical commercially available chlorinated polyolefins have a chlorine atom content of about 70% by mass, and adhesion of chlorinated polyolefin with the base material which is a PPS resin molded article is insufficient when a base material having such a high chlorine atom content is used.
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2002-97292
[Patent Document 2] Japanese Unexamined Patent Application, First Publication No. S59-145131 (lines 1 to 2 of the lower right column on page 2)